Glow discharge switch



Sept, 21, 1948. 7 o. J. H. ADMIRAAL 2,449,632

GLOW DISCHARGE SWITCH Filed D90. 5, 1946 I INVENTOR: DANIE. ,J. H, ADMIRAAL BY dM-s HIS ATTORNEY Patented Sept. 21, 1948 UNITED STATES PATENT OFFICE GLOW DISCHARGE SWITCH Application December 5, 1946, Serial No. 714,217 In the Netherlands February 13, 1946 7 Claim. (Cl. ZOO-113.5)

1 This invention relates to electric discharge devices of the type employing ionizable mediums such as gases or vapors, and more particularly to a thermal glow discharge switch for starting and operating said devices.

Heretofore, thermal glow discharge starter de vices or switches with at least one bimetallic actuated electrode were used as switches for controlling the starting of fluorescent discharge lamps having filamentary electrodes which require heating before starting a discharge therebetween. When a suitable potential is first applied to the switch, a glow discharge starts therein which heats a bimetallic member and causes it to flex. The flexing of the bimetallic member brings the switch contacts or electrodes into engagement to extinguish the discharge in the switch. Current flows through the electrodes of the lamp which are connected in series across the terminals of a current source by the switch. No further heat is generated in the glow discharge device or switch after the switch contacts engage each other. Thus, the heat sensitive parts of the starter device cool oil and its contacts separate again. This cooling off occurs rather rapidly so that the filamentary electrodes ofthe fluorescent discharge lamps may be insufliciently heated to support an electric discharge therebetween in 'spite of the fact that when the contacts oi the glow discharge device open an extra voltage surge is generated by a reactor connected in series with or parallel to the fluorescent discharge lamp.

As a result of this condition, the starter device repeats its starting attempts until the electrodes of the fluorescent discharge lamp have reached that temperature necessary'to support an electric The repeated attempts to ignite the discharge. fluorescent discharge lamp by means of insufilciently heated electrodes are detrimental to the life of these electrodes, and the light flashes occurring therewith are undesirable for lighting purposes.

An object of my invention is to provide a new and improved glow discharge switch which will provide the necessary time delay in the application of the starting voltage to insure an adequate initial heating of the electrodes of the electric discharge device.

Another object of my invention is to provide a new and improved glow switch including therein a pair of bimetallic members having different temperature-deflection characteristics and which support contacts and which flex in the same direction to contact one another, one of said members being of shorter length and constructed of thinner 2 laminations than the other whereby it possesses a greater unit deflection but smaller absolute deflection than the said other member.

A mrther object of my invention is to provide a new and improved glow switch including therewith a pair of bimetallic actuated contacts which when heated by the glow discharge move in the same direction, engage each other, and remain in engagement with each other over a part of the return motion during the cooling period.

Further features and advantages of my invention will appear from the following detailed description of species thereof.

Referring to the figure, the discharge device 1 therein comprises an elongated tubular or cylindrical envelope 2 having sealed into the ends thereof thermionic electrodes} and 4 which may be of the filamentary type each herein illustrated as comprising a coil, preferably in the form of a coiled coil of tungsten wire suitably activated, as example, with a usual mixture of barium and strontium oxides. The envelope 2 contains an ionizable medium. This ionizable medium may comprise a rare gas like krypton, neon, argon or mixtures thereof at a pressure of a few millimeters and a small quantity of mercury which, during operation of the lamp, has a low pressure of the order or ten microns. The device I may be a low pressure positive column lamp of the fluorescent type with a suitable phosphor which under the influence of an electric discharge through the ionizable medium produces fluorescence.

The device i is connected in series with a suitable ballast impedance in the form of a choke coil 5 and a starting switch 6 and connected across a suitable source of alternating current 1, 1'.

The starting or heating circuit 8 embodies start-- ing switch! in series with filamentary electrode .3, glow discharge device or switch 9, filamentary electrode 4, and choke coil 5. A capacitance iii of 0.01 microfarad rating is preferably connected ..a hermetically sealed glass envelope il, a pair of electrode structures l2 and i3 affording an electric discharge supporting surface and comprising thermally responsive bimetallic members H and I5, respectively welded to support wires l8 and I1, and an ionizable gaseous atmosphere therein such as neon at a pressure of 40 mm. at room temperature. A pair of suitable contacts such as tungsten contacts i8 and i9 mounted perpendicular to each other are fastened by suitable means to the ends of the bimetallic membcrs l4 and I5 respectively. The gap between these contacts at room temperature is about 0.75 mm.

In accordance with my invention, both electrodes of the glow discharge switch contain bimetal members which are mounted in such a manner and are of such dimensions that the contacts when the electrodes are heated by the glow discharge move in the same direction, engage each other and remain in engagement with each other over a part of the return motion during the cooling period as well as during part of the motion during heating.

This can be accomplished by making the bimetallic member of the electrode structure, which is in front in the sense of the motion that is caused by the heating, shorter and thinner than the bimetallic member or the other electrode structure. Thus, by means of varying the lengths of the bimetallic members the displacement are through which the free ends-oi the members move may be varied. By this means, the electrode structures are made to engage each other. If the shorter bimetallic member is also thinner than that of the other bimetallic member it will have a greater coeflicient of deflection, cool off quicker after engagement, and create an equal or greater force on the return travel than the longer bimetallic member. A means thereby is provided for the contacts to remain in engagement over part of the return motion during the cooling period. In this arrangement, it is advantageous if the shorter bimetallic member which is provided with a contact constitutes the free moving end of 'one electrode structure and is approximately one half the length and15 per cent thinner than the bimetallic member constituting part of the other electrode structure. For example, in a glow switch containing neon at a pressure of 40 mm. at room temperature the longer bimetallic member l4 may be 11 by 4 by 0.2 mm. and the shorter bimetallic member l5 may be 5 by 2 by 0.15 mm. in size and spaced between contacts a distance of 0.75 mm. at room temperature.

When the main switch 6 is closed, a glow discharge exists between electrode structures l2 and 43. The glow discharge may be aided by use of an activated surface such as one employing an oxide of an alkaline earth metal on at least one of the electrodes. This glow discharge causes the bimetallic members ll and I5 to flex in the same direction. The thickness of the laminations of member it, however, is larger than that of member l5, so that the change in shape of member it per unit length is less than that of member IS. The length of member I is,

however, so much greater than that of member i5 that the end of member l4 approaches engagement with member l5 after a travel of a few millimeters and thus the contacts I! and I8 engage each other. Thus, the opposite sides of the current source 1', I for the filamentary electrodes 3, l are conductively connected through the glow discharge switch I I, and limited by the reactor or choke coil 5. After engagement of the contacts l8 and IS the glow discharge becomes short circuited, thereby the bimetallic members I! and I5 loose their source of heat and begin to cool off. The thinner member l5 cools more rapidly than the thicker member ll so that the member i5 applies a pressure upon the member i4 and continues to do so over a part of the return travel of the electrode structures. When the contacts I! and i8 separate, the filamentary electrodes 3 and 4 have reached a sufliciently high temperature to support a discharge therebetween. For example, at a line voltage of 225 volts, the contacts l8 and I9 remain in engagement with each other for about two seconds. The glow discharge which precedes the engagement in this example lasts about two seconds.

The above described starting device offers advantages over and beyond the prior art arrangements. In many of the prior art devices, a contact corresponding to contact I9 is supported directly by the longer supporting wire I! without the mounting of bimetallic member IS in between and the contacts I! and I9 are separated about 1.5 mm. at room temperatures. when this glow discharge device of this conventional construction is used, the glow discharge lasts about 2 seconds until the contacts touch for the first time. The glow discharge device remains closed for about 0.1 second and after that repeats with a frequency of about per minute until the discharge tube ignites. During the time these repetitions occur, light flashes take place and radio reception in the neighborhood of the installation is disturbed by strong crashes, in spite of the presence or capacitor l0. When my glow discharge device is used, only one click can be heard when the contacts open.

It is obvious that the repeat ignition voltage of the glow discharge devices in both cases has been chosen larger than the operating voltage of the discharge tube I so that no glow discharge will take place in the glow discharge devices after the tube is ignited.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A glow switch of the discharge type comprising an envelope containing in ionizable medium and a pair of laminated bimetallic members each having a discharge supporting sur-- face, one of said members being substantially longer than the other and constructed of thicker laminations to produce rapid engagement be tween the members upon establishment of a glow discharge therebetween and to effect engagement therebetween during at least a part of the return travel during the cooling period by virtue of the difference in the respective temperature-deflection characteristics.

2. A glow switch of the discharge type comprising an envelope containing an ionizable medium and a pair of laminated bimetallic members each having a discharge supporting surface and supporting a contact, one of said members being substantially one half the length of the other bimetallic member and constructed of thinner laminations to produce rapid engagement between the members upon establishment of a glow discharge therebetween and to effect engagement between the contacts during at last a part or the return travel during the cooling period by virtue of the difference in respective temperature-deflection characteristics.

3. A glow switch of the discharge type comprising an envelope containing an ionizable medium and a pair of laminated bimetallic members each having a discharge supporting surface and supporting a contact, one of said elements being substantially shorter than the other bimetallic member and constructed of at least 15 per cent thinner laminations to produce rapid engagement between the members upon establishment of a glow discharge therebetween and to effect engagement between the contacts during at least a. part of the return travel during the cooling period y virtue rat the difference in respective temperture-deflection characteristics.

4. A glow switch of the discharge type comprisig an envelope containing an ionizable medium nd a pair of laminated bimetallic members each .avinga discharge supporting surface and carying a contact, one of said members being subtantially one half the length 01' the other bimetallic member and constructed of at least er cent thinner laminationsto produce rapid ngagement between the members upon establishrent of a glow discharge therebetween and to fiect engagement between the contacts during at east a part of the return travel during the coolag period by virtue of the difference in respective emperature-deflection characteristics.

5. A glow switchof the discharge type comrising an envelope containing neon at a pressure f 40 mm. at room temperature and a pair of lami- .ated bimetallic members each havingadischarge upporting surface and carrying a contact,- one of aid members being substantially longer than the ther and constructed of thicker laminations to 'roduce rapid engagement between the members lpon establishment of a glow discharge thereetween and to efiectengagement between the onta'cts during at least a part of the return travel luring the cooling period by virtue of the differnce in the respective temperature-deflection haracteristics.

6. A glow switch of the discharge type comrrising an envelope containing an inert gas and pair of lead-in wires supporting a pair of lamnated bimetallic members each having a dis- :harge supporting surface and carrying a contact, me of said members being substantially longer han the other and constructed of thicker lamina- Number Name Date 2,058,390 Alban et a1. Oct. 27, 1938 2,274,399- Cook Feb. 24, 1942 FOREIGN PATENTS Y Number Country Date tions to produce rapid engagement between the members upon establishment of a glow discharge therebetween and to effect engagement between the contacts during at least a part of the return travel during the cooling period by virtue of the difference in the respective temperature-deflection characteristics.

7. A glow switch of the discharge type comprising an envelope containing neon at a pres.- sure of 40 mm. at room temperature and a pair of lead-in wires supporting a pair of laminated bimetallic members each having a discharge supporting surface, one of said member a being 11 by 4 by 0.2 mm. in size and the other 5 by 2 by 0.15

mm. in size and the contact distance between REFERENCES orrao The following references are of record in the file of this patent:

UNITED STATES PATENTS 545,050 Great Britain ...May 8, 1942 

